A dash silencer is a large (approximately 1400 mm×700 mm) part generally that can be formed in a mat shape composed of fiber laminate such as felt and glass wool, or a porous synthetic resin material such as urethane foam. As shown in FIG. 11, through holes 100 for accommodating the steering column, the glove box, or the like, as well as numerous other mounting round holes 200, can be provided to the dash silencer. In an automobile assembly plant, an operator installs the dash silencer by bringing the silencer into the automobile cabin in a folded state and inserting stud pins into the round holes 200 which are provided to the passenger-compartment-side surface of the dash panel in advance. The round holes 200 can be made slightly larger than the diameter of the stud pins to make the installation operation easy.
In the inventions described in Patent Documents 1 and 2 below, instead of the round holes 200, cross-shaped, T-shaped, or horizontal-slot-shaped cuts are formed in the dash silencer, and the stud pins are inserted so that the cuts are pushed open, whereby the dash silencer is installed on the passenger-compartment-side surface of the dash panel.
Further, in the invention described in Patent Document 3 below, which is related to a patent application filed by this applicant, a chevron-shaped slit is formed in the dash silencer, and a stud pin is inserted through the slit to allow mounting.